DE102005057978A1 - Fermentation device with coupled substrate and sediment transport and method for operating the fermentation device - Google Patents

Abstract

A fermenter is described for biodegrading substrate containing organic material and for recovering the biogas produced during degradation. For the simultaneous circulation of the substrate in the fermentation device and for the discharge of deposited sediments, it is proposed to arrange stirring devices with transverse stirrer shafts (11) one behind the other in the fermentation device with axial distances which are smaller than the stirrer diameter. As a result, the stirring blades (7) of the stirring devices sweep an overlapping region (13) when the agitator shafts (11) rotate. At the bottom of the fermentation device sediment deposited is transported in this way from the front end to the discharge of the fermentation device.

Description

The The invention relates to a fermentation device for biological Degradation of organic material containing substrate and to obtain the The degradation of resulting biogas with an elongated closed container with a frontal insertion opening for the Substrate and a discharge opening for treated Substrate at the opposite End of the container and at least one exhaust vent for biogas, the container has multiple reaction volume cells, each individually several powered stirrers with circular moving agitators and across to the longitudinal extent of the container lying stirrer shafts for mixing the substrate, as well as a method for Operation of the fermentation device.

at the fermentation of organic material containing substrate, e.g. of biowaste, residues of food production or renewable raw materials one between the so-called wet fermentation and the so-called dry fermentation. While at wet fermentation a flowable suspension from the substrate prepared in a biogas reactor, e.g. a loop reactor with internal loop flow, treated when the substrate is dry fermented, e.g. at one end into one closed lying container introduced, by means of a stirring device circulated under biogas production and the treated substrate removed from the container at the other end.

The Method of dry fermentation are used alternatively to those of wet fermentation, if the anaerobic substrate to be treated is very rich in solids and therefore the necessary dilution into the operating range of the wet process with their solids concentrations of less than about 15% is uneconomic, or if the often necessary, but costly contaminant dumping in wet process for other procedural reasons not is required. dry fermentations are preferred at solids contents of equal to or less than 35% drove in the fermenter entry and can as standing or lying Reactors performed be.

One Advantage of dry fermentation when used in waste and residual waste treatment is the comparatively low treatment and conditioning costs for the assumed Input materials before fermentation. After a depletion of coarse impurities and subsequent comminution of the Fraction for the fermentation On 20 to 60 mm is usually before dosing in the fermentor no further contaminant rejection for e.g. Wood, plastic, glass as well as sand and stones necessary.

He buys This low technological effort for the application pretreatment with possible problems in the fermenter itself. Due to the biochemical conversion organic Compounds in the fermentation medium on the fermenter length decrease between the inlet opening and discharge opening the Solids concentrations of about 35% dry substandard on smaller as 20% dry substance and the viscosity of 30,000 to 60,000 mPas up to less than 5,000 mPas. Goods in the high-solids use the above mentioned sedimentable and floatable impurities distributed largely stable in position, they are characterized by the changing Material properties of the fermentation medium mobilized in the fermenter, which tends to lead to the formation of sinking and floating layers leads. The usual arranged in fermenters stirrers to improve mass transfer and media degassing support this fractional segregation still.

Therefore are found especially in horizontal dry fermenters in addition to stirring elements still special devices mainly for transport and Removal of sediments.

So are in the EP 0 617 120 B1 described special scrapers that transport the sediments to the reactor end in the direction of thinning medium on the fermenter bottom through movements transmitted via push rods.

at This known construction are so for the mixing and the Störstoffentnahme separate equipment needed which increases the technological and operational expenditure. Especially Carry out maintenance and troubleshooting Significant problems as they are associated with a shutdown of the fermenter could be.

Of the present invention is based on the object, a fermentation device of the type mentioned above and a method for operating the fermentation device in such a way that in addition to the actual homogenizing and degassing function the agitators without impairment the plug flow characteristic for the flow of solids between Fermenter entering and exiting a sediment movement at the same time Fermenterende induced and the formation of solidified floating ceilings repressed becomes.

These Task is according to the invention in the Fermentation solved by the fact that the stirrer shafts with center distances are arranged, which are smaller than the stirring diameter, so that the Agitator at Turn the agitator shafts over an overlap area.

The invention is based on the prior art, as in the EP 0 617 120 B1 beschrie ben is. This known fermentation device has separately controllable, transverse agitator units which disassemble the fermenter into a series of fictitious reaction volume cells (stirring cells) connected in series. The paddle wheel-like beam agitators effect a vertical media exchange in their respective agitating cell, including float-deck partitioning by the agitating bars emerging from the liquid, while the horizontal plug flow is generated by the combination of digestate removal and substrate dosing. The sediment transport takes place separately by means of a push frame. The agitator shafts are arranged in the fermenter in the fermenter in such a way that the distance between the stirrer shafts is greater than the stirrer diameter.

Out theoretical considerations, which confirmed experimentally have been, surprisingly shown that this stirring system also for used the targeted sediment transport along the bottom of the fermenter can be. This is the well-known by moving dunes effect of horizontal Displacement by material transport from the windward to the leeward side exploited. Transport vehicles are the stirring blades, which are designed accordingly Distance to the reactor bottom the sediments to a dune across to the longitudinal axis of the container push together. In the currently common Rührergeometrien and center distances this runs Transport process, however, ineffective and can come to a complete halt or even for trapping the agitators to lead dependent on of dry matter content, media viscosity and contaminant content.

In a particularly preferred embodiment of the invention, the stirring blades at their outer ends stir bar on that over the width of the container divided and arranged mutually offset. As shown has, should the sediment dunes stay small enough to be mobile. These are the stirring bars on the Divided reactor width and mutually preferred in angles below 120 degrees or 90 degrees offset on the stirrer shaft. In combination with the special geometry of the stirring system, where the agitator shafts with center distances are arranged, which are smaller than the stirrer diameter, the maximum height the sediment posing in the dead spaces between the rotating stir bar geometric in the desired Pretend manner. In the same direction of rotation of the adjacent agitators sediment is piled up on one side and off the staggered, meshing stir bar of the follower removed on the other side and transported across the ground to the next dune. Divided by the transversely divided and offset on the shaft stir bar it is avoided that the stirring bar on the full width at the same time immersed in the sediment and thereby to damage due to mechanical overload comes. Furthermore can no coarse material between the stirring bar and the container wall jam.

Conveniently, is in the discharge of fermentation a ground near suction arranged to deduct the transported there sediment. Especially for the Treatment of fermentation media with special sediment properties is according to a development of the inventive concept on site in the discharge area of the fermentation device a collection bag with sloping walls formed at the lowest point of the suction nozzle ends.

The The invention further relates to a method for biodegrading organic material containing substrate and to obtain the decomposing biogas produced, the substrate in a stretched longitudinal closed container introduced will, in the container flows through several reaction zones, in which it by means of individually driven agitators with circular around transverse to the longitudinal extent of the container lying axes moving agitator blades is circulated and degradation products from the container subtracted from.

the method, This object is achieved by the stirring blades of adjacent agitators, the with center distances are arranged, which are smaller than the stirring diameter, so controlled that the agitator on Gap work. This will ensure that the impellers of adjacent agitators do not block each other.

Preferably become the impellers adjacent agitators moved in the same direction. By the same direction of rotation is sediment piled up on one side and from the staggered, intermeshing stirring bar of the adjacent agitator removed on the other side and transported across the ground to the next dune.

The Invention is suitable for all fermentation equipment containing a horizontal container with transverse stirrers exhibit. Especially in the treatment of substrate, which has a high Sedimentierneigung possesses, the invention can with great advantage be applied.

Overall, a technically elegant solution for simultaneous mixing of Fermentationsgut and discharge of sediment deposited in the fermenter is provided with the invention with little investment. A particular advantage is that the plugs Current characteristic with respect to the substrate to be treated in the fermentation device is not disturbed by the Sedimentaustrag.

in the The invention is based on a schematic in the figure illustrated embodiment be explained in more detail.

The figure shows a fermentation device with a horizontal closed container 1 , the one at the front end an entry opening 2 for substrate to be treated and at the opposite end discharge openings 3 and 4 having. The substrate, which consists for example of biowaste or renewable raw materials, is fed via a feed screw 5 in the entry opening 2 of the container 1 brought in. In the container 1 are arranged transverse to the container axis stirring 6 arranged, each one aligned transversely to the container axis agitator shaft 11 which is driven individually. On the agitator blades of the agitators 6 are stirring bars 12 attached, which are divided over the container width and mutually offset at angles below 120 degrees on the agitator shaft are arranged. In addition, the stirrer shafts 11 arranged with axial spacings which are smaller than the stirrer diameter, so that there is a combing of the stirring bar 12 comes.

The overlapping area (combing zone) of adjacent agitators 6 is with the reference number 13 designated. By geometric definition of the center distances 6 as well as the stirrer diameter in the design phase, the maximum level of sediment launch can be determined 14 in the dead spaces between the rotating stirring bars 12 technologically pretend in the desired manner. In the same direction of rotation of the adjacent agitators 6 sediment is piled up on one side and removed by the staggered, intermeshing stirring bar of the following agitator on the other side and transported across the ground to the next dune. The biogas produced during the treatment in the tank is via an exhaust port 15 from the container 1 deducted. The sediment dunes transported to the end of the fermenter 14 arrive in the area of the discharge opening 4 where dry matter and sediment-enriched bottom fraction from the container 1 be sucked off. Low-solids liquid is in the upper region of the container via the discharge opening 3 dissipated. In a downstream container 16 Fermentation is separated and a dewatering press 18 fed. Deposited fermentation residues are finally via a derivative 19 withdrawn, while press water, for example as a liquid fertilizer via a line 20 is dissipated. Via a return line 17 Faulgut and press water to the front end of the container 1 if necessary, returned.

Claims (6)

Fermentation device for biodegrading substrate containing organic material and for recovering the biogas produced during the decomposition with an elongate closed container ( 1 ) with a frontal introduction opening ( 2 ) for the substrate and a discharge opening ( 3 . 4 ) for treated substrate at the opposite end of the container ( 1 ) and at least one exhaust vent ( 15 ) for biogas, the container ( 1 ) has a plurality of reaction volume cells each having a plurality of individually driven agitators ( 6 ) with circularly moving stirring blades ( 7 ) and transversely to the longitudinal extent of the container ( 1 ) agitator shafts ( 11 ) for mixing the substrate, characterized in that the agitator shafts ( 11 ) with center distances ( 7 ) are arranged, which are smaller than the stirrer diameter, so that the stirring vanes during rotation of the stirrer shafts ( 11 ) an overlap area ( 13 ). Fermentation device according to claim 1, characterized in that the agitating blades at their outer ends Rührbalken ( 12 ), which extend across the width of the container ( 1 ) are divided and arranged mutually offset. Fermentation device according to claim 1 or 2, characterized in that in the discharge region of the fermentation device, a ground-level suction nozzle ( 4 ) is arranged for the withdrawal of sediments. Fermentation device according to claim 3, characterized in that the container ( 1 ) in the discharge region of the fermentation device has a collecting pocket with inclined walls, at the lowest point of the suction nozzle ( 4 ) ends. A process for biodegrading substrate containing organic material and recovering the biogas produced during degradation, the substrate being placed in an elongate closed container (10). 1 ), in the container ( 1 ) flows through a plurality of reaction zones in which it by means of individually driven agitators ( 6 ) with a circle around transversely to the longitudinal extent of the container ( 1 ) axes ( 11 ) moving agitator blades is circulated and degradation products from the container ( 1 ), characterized in that the stirring blades of adjacent agitators ( 6 ), which are arranged with axial spacings smaller than the stirrer diameter, are controlled so that the stirring vanes work on a gap. A method according to claim 5, characterized in that the stirring blades of adjacent agitators ke 6 ) are moved in the same direction.